Genetic parameters and estimated breeding values of insect bite hypersensitivity in Belgian Warmblood horses.

Genetic factors involved in susceptibility to insect bite hypersensitivity (IBH) in Belgian Warmblood horses (BWP) were investigated. Data relating to 3409 horses were collected using a questionnaire, administered to owners during sport competitions, BWP breeding days, breeder visits and after phone calls. Horses were classified as IBH-affected or unaffected, based on two 'disease classifiers': a lifetime record, based on owner information (life_status) and another based on whether or not the horse was showing clinical signs at the time of questioning (clin_status). IBH prevalence was 10% based on life_status, and 6.2% based on clin_status. The heritabilities estimated using threshold animal models varied from 0.65 to 0.78 on the underlying scale (0.18-0.26 on the observed scale). These research findings indicate that susceptibility to IBH is a heritable trait in BWP.